A dark green hummingbird with a white throat is likely the White-throated Mountain-gem (Lampornis castaneoventris), a medium-sized hummingbird species found in the mountains of Costa Rica and western Panama. This hummingbird gets its name from the striking white patch on its throat which strongly contrasts against its overall glossy emerald green plumage. The white throat patch is key for identifying this particular hummingbird species.
Identifying the White-throated Mountain-gem
Several features stand out to help identify the White-throated Mountain-gem:
- Green plumage – The males have vivid emerald green feathers covering their head, back, wings, and tail. The green color comes from refracting feather layers that reflect light.
- White throat – A distinct white patch sits on the throat and upper chest, providing stark contrast against the jewel-toned green. The white area is more extensive in males.
- Red bill – Their short slim bill is bright red in coloration.
- Forked tail – Their tail is deeply forked like other hummingbirds.
- Small size – They measure 3.5-4 inches in length and weigh only 2-4 grams.
- High-altitude habitat – They live in high mountain cloud forests and scrublands at elevations between 6,500-10,500 feet.
The striking white throat is by far the most distinguishing feature and gives this species its common name. When glimpsed while feeding at flowers, the white throat immediately draws the eye. Females have less extensive white at the throat and more pale gray underparts overall. Juveniles lack the bold white patch entirely and have buffy edges to their plumage feathers until their first molt.
Appearance
With its vibrant emerald green plumage and distinctive white throat, the male White-throated Mountain-gem is an unmistakable sight. The crown and facial area are a rich blue-green fading to more yellow-tinged green on the rump and tail coverts. When sunlight strikes the feathers just right, the hummingbird can seem to glow from within. The green back grades into grayish underparts on the belly and undertail. The forked tail is black with an emerald spot down the center of each feather. In bright light, faint purple and teal highlights fleck the throat and breast.
Females, as in many hummingbird species, are less vividly colored than males. Their green upperparts are duller, and underparts are more broadly gray-white at the throat and belly with green restricted to the flanks. The tail remains blackish with an emerald spot on the inner webs. Immature birds lack any bright colors at all until their first molt. Before that, they have green edges to dusky brown plumage, and heavy brown spotting and streaking gives them excellent camouflage among vegetation.
Size and Shape
The White-throated Mountain-gem averages 3.5 to 4 inches in total length. Their wingspan reaches 5 inches across. Weights range from 2 to 4 grams, making them a mid-sized hummingbird species. The long slender bill measures around 0.9 inches in length and is perfectly adapted for accessing nectar from flowers. In shape, the Mountain-gem has a rounded head, short neck, compact body, and long tapered tail. The wings are broad like other hummingbirds suited for sustained hovering flight.
Habits and Behavior
This species has several interesting behavioral quirks related to its high mountain habitat:
- Aggressive – They aggressively defend flowering plants and feeding areas against other hummingbirds.
- Acrobatic – Their flight displays are exceptionally quick and acrobatic as they chase off intruders.
- Adaptable – They utilize a variety of brush and marginal woodlands at higher elevations than most hummingbirds.
- Hardy – They thrive at elevations too extreme for many other tropical birds.
- Seasonal movements – They undergo seasonal migrations to follow blooming flowers up and down the mountain slopes.
The White-throated Mountain-gem has a bold and feisty personality, reflecting the harsh conditions of its mountain home. This species vigorously defends feeding territories, aggressively driving away any trespassing hummingbirds that venture into their space. They perform elaborate display flights as part of their territorial behavior, making sharp back-and-forth movements and rapid hovering in place to issue their challenge. Their flight speed and aerial agility is breathtaking to observe.
They also have a remarkable ability to tolerate a range of cold and hot temperatures as they move across elevations seasonally. Expanding and retreating snowpack drives these altitudinal movements – they follow the nectar supply upslope during warmer months and descend when flowers become unavailable. Their metabolism adjusts to fuel their bodies in frigid overnight temperatures dipping below freezing.
Diet
Like all hummingbirds, nectar is the primary food source for White-throated Mountain-gems. They use their specialized tubular tongue to lap up sugary nectar from a variety of high altitude flowering plants. Some favorite nectar sources include the flowers of shrubs like fuchsia and datura, along with many species of bush penstemon. They supplement their diet with small insects and spiders captured on the wing or stolen from spider webs.
Reproduction
White-throated Mountain-gems breed between March and June in Costa Rica and Panama. As with other hummingbirds, males sing elaborative courtship songs and perform dramatic aerial displays to impress females. Once paired, the female builds a small cup nest out of plant down and spider webs on a branch or tree fern. She incubates the two tiny white eggs for 15-19 days until they hatch. Nestlings develop quickly on a diet of regurgitated insects and spiders. They leave the nest at 20-26 days old but remain dependent on the female for food up to two months, an exceptionally long period for hummingbirds.
Migration
Seasonal altitudinal movements are a hallmark of this species, as they migrate locally up and down the mountain slopes following the blooming of flowers. This pattern of short-distance migration allows them to take advantage of optimal nectar supplies without traveling far. Some populations may move as little as 500 feet between elevations while others migrate more substantially between 4,000-6,500 feet up and down the slopes.
Vocalizations
A sharp, ringing “chip” call is often given in flight or while perched. Males also have a thin twittering song of chirps and whistles used during courtship displays. Pieces of other species’ songs may get incorporated into their own vocalizations as well.
Range and Habitat
The White-throated Mountain-gem is limited to the highlands of Costa Rica and western Panama. Their range extends along the mountain chains running through these countries which create suitable island-like habitat. They occupy an elevation zone between approximately 6,500 to 10,500 feet above sea level.
This species inhabits mountain cloud forests and high-elevation elfin woodlands interspersed with scrub brush and clearings. They may be found along forest borders, second growth, and partially open areas. Flowering plants such as fuchsia, datura, and penstemon which provide nectar are vital habitat components. The presence of suitably fertile soils for nesting is also a habitat requirement.
Costa Rica
In Costa Rica, the species is common along the Cordillera de Tilarán, Cordillera Central, and Cordillera de Talamanca mountain chains. Some key protected areas such as Monteverde Cloud Forest Reserve and Tapanti National Park harbor good populations.
Panama
The Tanzanian Forest Reserve and highlands around the town of Boquete are strongholds for the species in western Panama. They range less extensively into central Panama along the Cordillera de Talamanca. Their distribution peters out before reaching the Panama Canal area.
Conservation Status
The White-throated Mountain-gem has a relatively small global range but remains common within its restricted highland habitat. Its populationTrends have likely been stable in recent years leading the IUCN Red List to classify the species as Least Concern. Some potential threats include deforestation at higher elevations and climate change effects, but these have not caused significant issues thus far.
Some specific conservation actions to benefit the White-throated Mountain-gem include:
- Protecting remaining stretches of mountain forest that provide habitat
- Maintaining connectivity between isolated highland areas
- Preventing further high-altitude deforestation from land conversion
- Monitoring for population declines
Protected areas like national parks and reserves are important for securing sufficient habitat. Linkages between fragmented habitat patches also help sustain connectivity. Ongoing monitoring is advisable to detect any future population declines that may warrant increased conservation action.
Costa Rica
Around 25% of the species’ potential range in Costa Rica falls within the boundaries of national parks, reserves, and wildlife refuges. These protected lands ensure habitat availability across parts of the three major mountain chains used.
Panama
A smaller proportion of protected lands exist across the species’ Panama distribution. Additional habitat protection here would be beneficial in maintaining populations into the future.
Taxonomy
The White-throated Mountain-gem was first described in 1860 by George Newbold Lawrence under the scientific name Trochilus castaneoventris. It has also been classified under the genera Heliomaster and Rhodopis at different times before being moved to its current genus Lampornis:
- Kingdom: Animalia
- Phylum: Chordata
- Class: Aves
- Order: Apodiformes
- Family: Trochilidae
- Genus: Lampornis
- Species: L. castaneoventris
No subspecies are currently recognized. Phylogenetically, its closest relatives are believed to be other high elevation tropical hummingbirds in the genera Heliangelus and Adelomyia.
Frequently Asked Questions
Where do White-throated Mountain-gems live?
White-throated Mountain-gems are found in the mountains of Costa Rica and western Panama at elevations between approximately 6,500-10,500 feet. They inhabit cloud forests and elfin woodlands in this highland habitat.
What do they eat?
These hummingbirds feed mainly on nectar from flowering mountain plants. They also eat small insects and spiders to obtain protein and other nutrients.
How can you identify them?
Males are unmistakable with vivid emerald green plumage above and white patches on the throat. Females are duller green overall with smaller throat patches. The red bill and vocalizations also aid identification.
How many eggs do they lay?
A typical White-throated Mountain-gem clutch contains just two small white eggs.
Why are they important ecologically?
As pollinators for high elevation flowers, these hummingbirds help maintain healthy plant communities and facilitate cross-pollination in the fragile mountaintop ecosystems where they live.
How fast can they fly?
Their rapid swooping flight allows them to reach estimated speeds of around 25-30 miles per hour.
Conclusion
With its stunning emerald and white plumage set against the lush cloud forests of Costa Rica and Panama, the White-throated Mountain-gem is a dazzling tropical hummingbird. This species exhibits specialized behaviors like seasonal migrations across elevation zones and defending mountain flowers aggressively. While limited in range, populations appear stable within protected highland habitats. The White-throated Mountain-gem provides an iconic symbol of the biodiversity found in the northern Andes region. Its unique attributes allow this small green-and-white hummingbird to thrive in its extreme montane environment.
